Nick Andrew <nick@xxxxxxxxxxxxxxx> writes:
> Exiting a process from within a callback function seems to me to violate
> the principle of least surprise.
Huh? Who is surprised?
I do not know who taught you that "do not exit in a callback" dogma, but I
suspect it was misrepresented when it was taught to you.
A library that calls your function back could be structured this way:
lib() {
perform some set-up that affects external world;
call your callback function;
clean-up the effect of previous set-up action;
}
and exiting from your callback function is not a good idea as it prevents
the library from doing the necessary clean-up in such a case.
But that is true just in a(n extremely) general case. Your generalization
is not particularly useful, methinks, and use of exit(0) in the patch is
very well justified (rather, I do not think they even need justifying).
- The callback you are looking at is not a general purpose callback for
other program's use, but written for a specific use of rev-list;
- The purpose of that exit(0) is to signal "there is something" as
quickly as possible, which was what you wanted out of rev-list;
- Revision traversal is a read-only operation and we know that there is
no externally visible set-up done in the function you are calling to
get your callback called, that needs cleaning up later --- this is not
expected to change, as there are longstanding existing callback
functions supplied to traverse_commit_list() that die() upon seeing
errors already.
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